Slide-type calculator



Nov. 17, 1953 F. H. BRICKNER SLIDE-TYPE CALCULATOR 4 Sheets-Sheet l Filed June 9, 1952 NNY NNI

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Nov. 17, 1953 F. H. BRICKNER 2,

SLIDE-TYPE CALCULATOR Filed June 9, 1952 4 Sheets-Sheet 3 mw MN Nov. 17, 1953 F. H. BRICKNER SLIDE-TYPE CALCULATOR 4 Sheets-Sheet 4 Filed June 9, 1952 FRAN/f H. amc/wen,

INVENTOR.

HUEBNER, BEEHLE'R, WORRE'L HERZ/G,

@y ATTORNEYS.

Patented Nov. 17, 1953 UNITED STATES PAT EN T QFFICE 4112 Claims. l

This invention relates to` calculators,l andrnore particularly to calculators forv ascertaining the monthly interest dueon any ramount of principal at a predetermined annual interestk rate;

itis an object of this invention to provide an interest calculator in which, forv aV predetermined interest rate, the principal may be inserted into the calculator; and the interest read direct without requiring ancillary calculations on thel able-slide type, such as may be made of card-Y hoard or plastic, in which the principal may hek inserted into the calculator, and the interest yread directly without ancillary calculationsorrepositioning oi any slide.

In accordance with these and with other ohjects which will become apparent hereinafter, the instant invention will now he described.

interest calculators ofthe flat, slide type have long been known in the art. They consistr generally of a lat'cardlooardienvelope having aplurality or" windows'in thecover, and severalslides orsliders which may he, movedV so asitov register their numbers with the windows in the cover. Suchprior calculators, however, have' the shortcoming of requiring' ancillary calculations by the operator, generally additions. For example, a common form of such calculator has a rst slider for the thousands portion of the` principal, a

second slider for the hundreds, a third for the tens, and a fourth for the units. By appropriate manipulation, the operator is able to ascertain how much interest is due on the thousands porr tion of the principal, how much on the hundreds,- how much on the tens,v andhow much on the units. However, he must then add up the four interest portions to obtain the total.

In accordance with the instant invention, ,a dat,

envelope-type calculator is provided in which no ancillary or after calculations are required. The operator causes the principal to be appropriately registered in the calculator, and 'then ythe interest is read off directly as a single total. This isimade possible in the instant invention by the use of shutters. secured laterally to the sliders, shutters overlie the adjacent sliders so ask block out certain numbers on the adjacent slider. The shutters have windows therein selectively positioned so as to allow only the proper ligure to be read from 'the said adjacent sli In this way correlation is achieved between jacent digit columns, for example between the tens, and the hundreds and the units.

In general, this shutter modulation or control isrequired in order to allow the hundreds slider, for example, to control a reading which would normally appear on the tens slider. lioivever, for complete uniqueness of answer, and to completely ohviate requiring any subsequent repositioning ci any slider, the hundreds slider is also novidcd with a second shutter which overlies the tliou sands' slider above it. This shutter also has a pair. of oppositely spaced elongate windows to selectively coverand uncover portions of the thousands slider. In thisway, a particular reading on the hundreds slider is under the control oi' thepositioning of three different sliders, namely, the hundreds slider itself, the thousands slider above it, and the tens slider below it.

A particular embodiment of the instant invention will now be described with reference to the accompanying drawings, wherein:

Fig. 1 is a plan View of the assembled calculator;

Fig. 2Y is an end view;

Fig. 3 is a view similar toFig. 1, with the cover of the enveloperemoved to reveal the sliders disposed therein;

Fig. iV is a cross sectionv taken on line :i4-Ji of Fig. 3;

Fig.V 5 is a fragmentary view with portions of the cover broken away to illustrate operation of the device;

Fig. 6 is a View similar to FigA 5, illustrating another operation;

Fig. 7 is an` exploded isometric View showing the various parts of the calculator; and

Fig.,8 is an isometric View showing a typical slider with its superjacent shutter, and its pendent suhjacent shutter.

Referring to Fig. 1, l! designates a nat rectangular envelope comprised principally oi a cover l2 and a back i3. The cover i2 is spaced from the 'hack` i3 by edge walls Hi, which enclose threeedges of theY envelope, leaving the fourth edge loopen. The walls itrnay he forniedintegral with the back I3 if convenient, would be the case where the device is made of plastic or resinous material. if made of cardboard, the

walls are secured to the back I3, and the cover I2 is in turn secured at its edges to the walls I4, as shown in Fig. 2. Three elongate spacers I1 are secured to, or formed integral with, the bach I3 within the envelope I I, and extend transversely away from the open edge I6 of the envelope. The spacers are not as high as the edge walls I4, so that a slight clearance is left between the 'top of the spacers I1 and the under side of the cover` I2. The spacers I1 and walls I4 cooperate with the back I3 to form guideways or slideways for a plurality of hat elongate sliders I8, I9, 2 I, and 22. The slider I8 is the thousands slider, since it is the slider on which the thousands column of the principal is enumerated. Similarly, the slider I9 is the hundreds slider, the slider 2| is the tens slider, and the slider 22 is the units slider.

In the particular embodiment shown in the drawings, the calculator is capable of calculating interest for both 6% loans and 5% loans. Calculation of monthly interest at a 6% rate is much simpler arithmetically than at and this is reflected in a simpler construction of the calculator. Therefore, that portion of the calculator will first be described.

As shown in the drawings, the cover I2 has a rst line of four windows spaced thereacross transversely of the sliders. The windows in the line 25 are disposed to register with a respective one of the four sliders. Each window in the line 25 is of sufficient length to register with only one row of figures on each of the sliders. This is mentioned at this time because this characteristic of the 6% window of line 25 is different from the more complex 5% window line 69, where some of the windows must be made longer so as to register selectively with six rows on a slider.

An annual interest of 6% corresponds to a monthly interest of .5%. When .5 is multiplied with any number whatever, the answer must terminate in either zero or five. This fact simplies the construction of the interest portion of the calculator for 6% calculations.

Consider rst the thousands slider I8 shown in Figs. 3 and '7. On this slider are placed four rows of numbers 23, 24, 26, and 21. Rows 23 and 24 are principal numbers, while rows 26 and 21 are interest numbers. Row 24 and row 2E happen to be aligned, but this is not essential to the construction of the calclulator, since the row 24 is a row of principal gures, and the row 26 is a row of interest iigures. They are aligned simply to conserve space.

Only the rows 23 and 21 are used in the 6% principal calculations. Row 23 is positioned so that the figures therein may be selectively registered with the window 28 in the 6% line of windows 25. The line 25 is read from top to bottom, as are the other window lines in the calculator. Spaced from the 6% line of windows 25 and transversely of the sliders, is a line of interest windows 29 with which may be selectively registered the interest rows of numbers on the sliders. The first window 3l in this line is elongate so as to span both the row 26 and the row 21 of interest figures. For 6% calculations only the upper portion of the window 3I, opposite the row 21, is employed, the lower portion being continuously covered by a shutter 3B to be described hereinafter.

The rst window 3| in the line 29 of interest windows represents tens of dollars of interest. The rows 23 and 21 are so correlated on the slider I8 with the windows 28 and 3I that the digit appearing at the window 3l shows the number of f slider ill.

tens of dollars of interest due for any given thousand dollars of principal appearing at window 26. hor example, when the l in the row 23 is registered with the window 26, a 0 in the row 221 is registered with the window 3l. This is because the interest on 251,990 is less than $10, and hence there is no possibility oi' anything more ythan a 0 being needeh at the window 3l. When the 2 in the row is registered with the window 28, the iirst l in the row is registered with the window 3l, because the interest at 6% on $2,000 is $10, and the interest on $2,999 is less than $20.

The hundreds slider lll is constructed in a manner somewhat similar to that of the thousands The bottom row of figures Et registers with 'the opening 36 in the cover, which is the second opening in the 6% window line 25. Although the slider' has six other rows of hgures, 5t, and they are not used in Ithe 6% calculations, but are used only in the calculations to be described hereinafter.

The slider ill also has tour rows of interest iigures and 60. Only the top two rows 32 and 36 are employed in the 6% calculations. The window in the interest row oi windows 23 in the cover is long enough to reveal each of the four rows 06, and 33, but the bottom two rows and are liept covered during the 6% calculations by a superjacent slider to be described hereinaiter. The principal numbers in the row Cooperate with the interest numbers in the row in a manner substantially the same as ythe cooperation between the rows 23 and 2l on the slider i6.

nterrelation between the thousands slider I3 and the hundreds slider I6 is effected by the use o1 a shutter which is secured laterally to (preferably formed integrally7 with) the slider I8. The shutter ill overlies the slider i9, -that is to say, is interposed between the slider I9 and the cover I2, as seen in lli-ig. li. The shutter ti does not cover any of the numbers in the row 32, but it does cover the interest rows 34 and 36. Shutter 4I has a plurality of windows d2 which may be selectively registered with the numbers in the rows 3ft and 36. As seen in Figs. 3 and 7, the windows 42 are staggered so that a number in either the row 34 or the row is exposed through the cover window 30, but both rows are never exposed at once.

The purpose oi the shutter Ill is to rerlect into the answer the effect, cn the units column of the interest (window of a change in the thousands column of principal (window 23). At 6% 'this change occurs in multiples of iive; and this -fact simplies the construction of the calculator, for it is only necessary to make each number in row differ by live from the adjacent number in the row 66. Then, by the shutter AI, the appropriate unit dollars answer uncovered either from the row or the rot For example, when all the sliders are positionet to the lett, the number .$50000 appears in the 6% window line reading from top to bottom, and the number $00.00 appears in the interest window line 29. When the thousands slider I8 is moved to the right until 'the number l row 23 appears at the window the shutter fl! is caused to move so as to cover up the nrst 0 in the row 34, previ ously exposed through the window 30, and to uncover the adjacent number 5 in the row 36. Meanwhile, the first 0 in row 21 has been replaced by the third 0 in the row. This accordingly indicates an interest of $05.00 per month on a loan of $1,000 at 6%, which is the correct answer. Moving;` the thousands sliderl ltiurther; to. the rightl operates in a similar manner,V each4 digit incre-V mentserving to either uncover a 5 and blank a 0 on the sliderA I9, orv to blank outa 5 anduncover a 0, while. simultaneously increasing the` number appearing at the windowhwithevery, other digitk increment of principal..v

Asnotedhereinbefore, the, rows z'i and. 3S are continually blanked out by another shutter 43 attached to (preferably formed integrally with) thetensslider 2 I While the shutter 43 doeshave anY elongate window. 98` (Fig. 7.) capable of being registered with the window 39, the slider 2l is not pulled far enough out during 6% calculations to expose the window 98 to the window 39. The purpose of the shutter 43will be explained hereinafter in connection with. the` 5% loan calculations. If only 6% calculations are desired the shutter 4.3.is not needed.

The hundreds slider I9 is related to the tensA slider, 2i. inthe same way that the thousands slider it is related to the hundreds slider I9. Thatis tosay, the hundreds slider I0 has secured laterally thereto ay shutter lill` which overlies the tens slider 2l and. has a plurality of windows 46- whichr selectively blank and uncover interest numbers that differ by five, on the tens slider 2I Likewise, the tens slider 2 I has a shutter 41 which overlies the interest portion of the slider 22. As noted, none of the shutters 4I, 44, or il covers any portion of thev 6% principal rows of numbers 32, 5I, or 56.

By.l way. of example, let it besupposed that it is. desired. to ascertain the monthly interest on a 6% loanof $2,345. The thousands slider I8 is pulled. out untilthe number 2 in the row 23 registers ywith the window 28. This indicates an interest of $10.00 per month. When the hundreds slider I9 is pulled out until thenumeral 3 in the row 32 registerswith the window 33, the second of the numerals. 1` in the row 34 registers with the window 45: in the shutter 4I and with the window 30, This. operation also moves the shutter 44. until the row` 48 on the tens slider 2l is seen through the cover Window 49 and the shutter window 150. In this case the number 5 in the rowv 1.1.0 will be seen. When the tens slider 2| is moved until the number 4 in the row 5I registers. with` the window 52 in the cover, it causes the number 5 in rown 4l! to bereplaced by the iirst number 'l in the row. It also positions the shutter lll so thatthe row 53\on thev slider 22 is exposed through the cover Window 54 and the shutter window 5.0. Finally, when thenumber 5 in the row 56 is registeredV with the window 5l, the lirst number 3 in the row` 53 is brought into registry with thewindows 5'4 and 50. Thus the monthly interest on a 6% loan @$2,345- is indicated to be $11.73.

Construction of the calculator to also indicate monthly interest at 5% is more complex. The interest ilgures indicated by the slidersV go up in incrementsy olk rive. Thus movementy of the` slider 2i causes the calculator` reading toincrease in steps or'increments of$.05` startingat $.05, $.10, $.15, etc. Similarly, movementofvthe 61 slider I9 causes; the.; calculator readingl ta soun in increments. of. $.50.. Likewise;thencremental increase in the interest; line. of windows29 profL duced by movementof the thousands.; slider I3 is, $5; going: up incrementally through. $5.00,- $10.00, $15.00, etc. suited. to calculations ofj 6%v loans because,r f or example, foreach $10y increase in principaL the.

interest increases $.05'. Thus movement, ofthe; slider 2i tdincrease the reading` in theiprincipalj, line 25V in increments of $10 causesitheL interest, reading inthe window 1ine29. to inoreasemin-v crements of $.05.

To accommodate; these interest figures to- 5%-, interestis more complex, becauseave centrincreaseA inr interest: isl brought..ajbout.notr.by an. increase of. $1.0 in the principal-but; by anzin-y crease oi.v $12. Similarly, fifty, cents interest; on; a. 5% loan isy brought about` not by, $100 prin.- cipal, asin the case of. a5% loan..b.ut byl afprincipal of $120. IThe problem then is to distribute the principal numbers which appear atthewindow line 5S- so. that the operatorie required; tov position the sliders, in effect, in increments of.l twelve rather than in increments of ten. This will be illustrated hereinafter.

To accommodate the calculator for-5%. loans, each of the sliders I9, 2|, and. 22 is provided. with six separate. rowsof principal figures, exempliiied by the rows 52, 59, lil, 52, 63, and Eil (Fig. 'il on the slider i9. Even this` isl short of the number that might. possibly. be re. quired, since there is. a. certain` correspondence between. multiples ork 10 and multiples of 12'. In. the general oasev of providing for any multi. plier whatever it might 'be necessary` to provideten such rows of numbersv tov accommodate the calculation. is mentioned before, six rows are: sufcient here because the number 60 `is al com-l mon factor to both 12 and 10, and thus it is nec-- essa-ry to provide rowsonly for the factors: 0, l2,

36, 48, and 60. Starting with 72 the seriesV repeats itself, this being the sum of GOIand 12.

Inthe case of the 5%. principal, the: row 24'- on the thousands slider I8 is employed instead ofv the row. 23, which is used for thel 6%` principal. Thus the window 65.. of the 5% line 691 in the-A cover l2registers only with therow24.

To accommodate the six rows 58-.64n on the. hundreds slider I9, the hundredsfwindow'l in the line 60 is made long enough so that-it spans all of the six rows. It is a: function of the shut-4 ter 4I on the thousands slider- I 8 to selectively uncover only one of the rows 58,-64 at a time, this being done bythe windows 68A in the shuter 4I..

in the case of a 5% loan, the lowest factor commonl to lboth 1000 and 1200 is 6000. Thus the windows 68 inthe shutter 4I. are so spacedL that when the slider I8v4 ismoved to the right, thereby covering the4 originally visible 0 in the row 5.1i, no other numbers on: theslider I9A are uncovered until the number 6 in the row'24 reg-r isters with the window 55. At this point ther-0 in the row 64 is again uncovered. For any. exact thousand-dollar loan between 0- and 6000, it isn necessarir to move the hundreds slider I9I in order to bring. a0 .on one of the rows 58, 59, 6 I, 52, or @tinto registration. Asbest seenin Fig, 3, the windows 53. in the shutter 4I are staggered and spaced diagonally across the shutter so that each incremental movement of the slider I8 bringsthe-next adjacent -rowoffigures E13-til into registry with the elongate Window 67' in` the" cover'I2.

Theseincrements are. well..

estates The criteria for spacing the Windows in the shutter 4l and for spacing the numbers in the rows 5ft-G4 may be best understood by discussion of a particular example-for instance, the calculation of one months interest on $1000 at 5% per year, illustrated in Fig. 6.

Starting with all the sliders pushed to the left, the figure $0000 appears in the 5% Window line E9. Similarly the interest indicated in the window line 2S is $00.00. When the thousands slider I3 is moved to the right until the numeral l in row 24 registers with the window 66, the second 0 in the top interest row 2l is brought into registry with the cover window 3|. The associated movement ci the shutter lll, secured to the slider lil, causes the nrst Window 'il of the window row t2 overlying the interest row 34 to move one increinent to the right. This Window 'l l, however, is two increments wide, so that the row 34 is still exposed through the interest Window 39. 'Ihus there have yet been no changes made in the interest reading by movement of the thousands slider l to bring the numeral l in the row 24 into registry with the window '66.

Such movement, however, has moved the window l2 in the shutter lll away from the 0 in the number row Gt and caused the window 13, aligned with the row 50, to register with the cover uindow Gl. W ith the slider lil in its lefthand position there is then no number seen through the registered windows G1 and 'I3-only the face ci' the slider Is is seen. It is preferred to niark the slider lil at this point with a small arrow directed to the right to indicate to the user that the slider i0 must be pulled to the right until a number registers with the windows 6l and :Such arrows are placed over the surface of each slider, as shown at 50 in Fig. 7, wherever the slider is to be pulled out to bring a number into registry.

The slider le is then pulled to the right until the numeral 0 in the row 58 registers with the windows i3 and El as shown in Fig. 6. In this position the first numeral 4 in the interest row 34 has been brought into registry with the win dow's 33 and il, so that the interest coluinn now indicates $04.00. $4 per month is the interest payable on a loan of $960 at 5% per year. This leaves $40 to be accounted for.

Movement oi the hundreds slider I3 to the position shown in 4Fig. 6 has caused its associated shutter iii to now cover up the 0 in the row 1li, previously o rvable through the windows 'it and "Vi in tl cover l2 and shutter 44, respectively; a-nd has 4'brought the window 'i8 into registry with 'the cover window TG. This window 'i8 is aligned with the number row 'i9 on the tens slider 2l, and in 'the position thus far explained there is no figure at this point in the row i9. As explained above, a small arrow pointing to the right is marked on the slider 2i to indicate that it must be pulled to the right until a number is observable, this number being the 0 in the row 'i il on the slider 2 l.

ith this movement oi the slider 2i, the second oi the numbers l in the row 8l on the slider 2i has been brought into registry With the cover window iii and with the Window l' in the shutter 'The interest line of windows 2s now indicates an interest of $04.15, movement of the shutter fil having shifted the interestreading from the top row to the bottom row 82 on the slider 22. The 5% principal window line 09 now shows $100X, X indicating a small rightwardly directed arrow, as described above, on the slider 22, ndi- 8 eating that the slider 22 must be moved to the right to bring a number into registry with the window 83 in the cover l2 and with the window 84 in the slider 4l.

$4.15 is the interest on $996 at 5% this leaves $4 to be accounted ior. This is done by moving the units slider 22 to the right until 'the 0 in the row et registers with the Windows and S3. This brings the nrst number 7 in the row lili on 'the slider 22 into registry with the Windows il and 535i. There is thus indicated an interest oi $04.17, which is the monthly interest on the $1000 principal now indicated in the 5% line oi' windows G9.

Thus simply by registering the proper digits in the four columns o1 the interest line the operator has obtained directly and without any further calculations or slide movements, the interest due-$4.17.

ln making these calculations it will be seen that it is necessary to eiiect manipulation of the calculator in such inorei'nents oi principal that the interest ends in either 0 or Thus the first factor of principal was taken care oi in the calculations was $980, which calls i'or a incnthly interest oi exactly $4.00. The next principal i'actor which was accommodated was i536, which calls for a monthly interest of fifteen cents. The dnal four cents was accommodated entirely by the units slider iurther exemplify the manner in which the 5 00 principal is broken down into its component parts of 960 plus 36 plus l, let it be iirst imagined that the calculator is in the position shown in Fig. G. The number 0 is seen through the window but this 0 does not represent the proportional or true Zero starting point of the units slider By pushing the tens slider 2l in all the way to the left, there is brought into view through the window the number in the row on the slider iil, thus indicating that the actual positioning oi the slider 2s is really proportional to the portion of the 31000 principal, and that it has been forced by the shutter Iii' to be moved out to malte vthis indication.

Similarly with the sliders in the position shown in Fig. 6, let the hundreds slider i0 be moved in to the left. This now blanks out the 0 in row is, which was previously visible through the window lli, and brings into view the numeral l in the row 'iii on the slider 2i. This shows that the slider 2i was actually in a position corresponding to teil, this being the first tens digit above $30, and hence proportional to the component of the total. The tens slider 2i was forced outward, in effect, by the interposition oi the shutter 44, in order to acconiinodate 'this $36 con1- ponent.

Finally, again starting with the sliders in the position shown in Fig. 6, let the slider be pushed in to the lei't. This causes the shutter 4| to blank out the 0 previously row 58, and brings the window in th` 4I into registry with the cover windo" There is no number on the slider new registering with these windows, but it will be noted that the slider i9 is now positioned one increment beyond the numeral 9 in the row ill (see 7). Thus in fact, the slider is has been moved out a distance proportional 'to $960.

It is thus seen that the function of the pendent shutters 4l, 44, and il is to iorce the next lower slider to be moved out a distance proportional to that portion of the principal which it must account for in the interest line 29.

The example of a $2000 principal at 5% is also principal, with its corresponding three cents Lshow .the purpose and function or" 'the upper .shutter 4I secured to the slider ofthe calculator will new be discussed. vithat itis 'desired to ascertain the monthly inuseful toillustrate lthis invention. y.Assume that .the sliders :have been positioned so that a principal iof $2000 is indicated in the 5% line of 'windows 39. As pointed out hereinbefore, it is "a function of the calculator to, in eiiect, break down this $2000 principal into increments, each of which calls 'for an interest ending in either or 5. The rst breakdown is effected by the slider I8, which breaks the principal down into $1200 plus $800.

The next breakdown is eiiected by the slider I9, which breaks the $800 into iactors of $720 plus $80. The next breakdown is veffected by the slider 2l, which breaks the $90 down into $72 plus $8.

This may be illustrated by positioning the calculator so that $2000 appears in the principal line 69. The interest reading is When the thousands slider I0 is moved fully in, to the left, the reading in the principal line 39 becomes $0800, and the reading in the interest line 29 becomes $03.33. This indicates that 'previously kthe thousands slider I3 had actually been positioned vto accommodate $1200 or principal, with its `corresponding $5 ci interest, leaving the re- `maining $800 for the other three sliders i3, 2i, v'and 22.

When 'the hundreds slider I9 is moved fully to the left, the reading in the principal line di? is changed to $0080, and in the interest line to $00.33. This shows that the hundreds slider I9 was actually positioned to accommodate $720 and its corresponding $3 of interest, leaving the `remaining $80 to be taken care of by the sliders 2| :and 22.

'.Finally, when the tens slider 2| is moved rulli interest.

The dollars slider 22 thus took care of $9 of oi interest.

Another example will now be considered to or superjacent shutters 43, 30, and 95. As best seen in Fig. 8, the superjacent shutter 43 extends laterally 'to one side of the slider 2l, while the pendent shutter il extends laterally to the vother iside thereof. The shutter 53 (Fig. 3) is interposed between the slider i9 and the larger The shutter 43 is accommodated by the formation ci a slot 89 along the junction between the slider i9 and its pendent shutter 44. A connecting tab iii extends between the slider 2i and the shutter 43, passing through the slot The slot 239 has 'a 'homologue in the slot between the slider 2l and vits 'pendent shutter .4?.

Asbe'stseen in Fig. 3, the slider 2 i, its pendent @shutter 4'I, and its superjacent shutter 43 are pre'ierably formed'integral, of one piece of sheet material such as plastic or cardboard, although if .desired they maybe made separately and securedtOgether.

By -way of illustration, another example of use Assume 'terestat 5% on a principal of $8674. The thourepresents va tiny arrow directed to the right.

"This arrow is in the row 59 on the slider i3 and is visible through the window 93 in the shutter 4I.. The interest line 29 now reads $30. $30 is the monthly interest, at 5%, on a principal of $7,200. This leaves $1,474 of principal which must be accounted for by the remaining three sliders I9, 2l, and 22. The interest on $1474 is $6.14.

The slider `i9 is now slid to the right until the numeral 6 in the row 59 registers with the window kti'l in the cover I2, and with the window .93 in the shutter 4I, which had previously been registered with the window 6T by movement of the slider I3. The principal line 69 now reads $86X0 with X representing a small arrow directed to the right in the row 94 on the slider 2l visible through the window 96 in the shutter 44 .and the window "I6 in the cover I2. The interestline 29 reads $35.50. This is the monthly interest on a 5% loan of $8,520, leaving $154 which must vbe `accounted. for by the remaining sliders 2-I and`22.

The monthly interest on $154 at 5% is 64 cents. This added to the present interest standing of $35.50 gives $36.14. We thus know that the final answer must read $36.14, yet the hundreds slider I9 has already been positioned to indicate only $35. Therefore, means must be provided to either force the operator to readjust the hundreds slider I9, or to automatically change the 5, appearing at the window 39 to a 6. Since one of the purposes of this invention is to simplify use of the device to the maximum, the super-shutters 30, 43, and have been provided. It is the function of these shutters, for example the shutter 43, to automatically cause the number appearing at the interest windows, for example the window v39, to be raised by one digit, whenever the calculated interest requires that a number be carried over to the next addition column.

With the sliders I8 and I9 .in the positions explained hereinbefore, let the tens slider 2I be slowly slid to the right. When the principal in the window line 69 reads 863K, the point has been reached where no further interest can be indicated properly unless the dollars digit in the interest, i. e., at the window 39 is increased by one. This is because the .interest on the next increment, namely on $8,640 is $36.

.As the tens slider 2| is pulled further to the right, so that the 3 at the window 16 changes to a 4, the corresponding movement of the shutter 43 causes the upper window 91 (Fig. 7) in the shutter 43 to move out of registry with the cover window 39 and simultaneously ybrings into registry .the lower window 98. This shifts the reading on the slider I9 from the top pair of rows 34 and v30 down to the bottom pair of rows 3l and 38, which, it will be noticed, are .in certain cases one digit higherthan the corresponding numerals in .the top .rows 34 and. 39. Specifically, .in this example, the last of .the numerals 5 in the row 34, which was previously visible at the window 39, through the window 106 in the shutter 4I, is now blanked out `by the `shutter 43, and the irst of the numerals 6 in therow 31 is brought into view at .the window 39 through the window Ili! in the shutter 4I. Simultaneously the 9 in the row 48 previously visible at the window 49 is now replaced lby the adjacent 0 in the row. It is thus seen that the break or transfer from the upper window 9! ,to thelower window 98 in the shutter 43, as represented bythe window edges 99, is directly aligned with the point at which the numorals on the supporting slider Y2| `shift from 9 to 0 (see Fig. 8).

In this manner, changes in the lower columns of digits as, for example, in the tens column, are reflected baci; into the hundred column.

Proceeding with the example in question, when the tens slider 2| has been positioned so that the numeral 7 in the row 94 is visible through the window 13 of the cover l2 and through the window 96 of the shutter 44, the principal line 69 reads 867K, Where X represents a small rightwardly directed arrow in the row on the slider 22 visible through the window |02 of the shutter 41. The interest in line 29 now reads $36.10, this being the interest due on a loan of $0,564. This leaves which must be accounted for by the units slider 22.

When the units slider 22 is pulled to the right until the numeral 4 in the row |0| is visible at the window 03 through the shutter window |02, the second of the numerals 4 in the interest row 53 on the slider 22 is visible at the window 54 through the window |03 of the shutter 41. This completes the calculation, the interest on $8,674 being, to the nearest cent, $36.14.

The superjacent shutters 30, 43, and are not absolutely necessary to practice important features of the instant invention. If they are not provided, it is merely necessary to mark a small arrow on the slider to indicate that it must be moved one increment to the right in order to bring about an increase of one digit, and thus accommodate the shift discussed above.

The above example of a loan of $8674 at 5% also illustrates (as will any example, for that matter), how the calculator for 5% loans breaks the total principal down into factors divisible by 12, 120, 1200, etc. 3674 is the sum of 7200, 1320, 144, and 10. 7200 is exactly divisible by 1200 and gives an interest of $30; 1320 is exactly divisible by and gives an interest of $5.50; 144 is exactly divisible by 12 and gives an interest of $.60; and 10 is the remainder with an interest of $.04.

With the calculator manipulated to show a readingr in the principal line 69 of $8674, the in'- terest indicated is $36.14. If the thousands slider I8 is now pushed fully in. to the left. the reading in the line 03 becomes $0X74, where X indicated a blank; and the interest reading in the line 29 becomes $06.14. By moving the hundreds slider I9 in. to the left, increment by increment, it may be seen that it was actually positioned live increments beyond the numeral 9 in the row 63. This corresponds in distance to the number 14. Thus it is seen that the three sliders I9, 2|, and 22 actually take care of $1400 plus $74 or $1474. This $1474, subtracted from the original $8674 shows that the thousands slider was actually taking care of $7200, with its corresponding $30 of interest.

New when the hundreds slider i9 is pushed in, to the left, the principal reading in the line E9 becomes $00X4, and the interest reading becomes 300.64. The blanl; space on the slider 2|. indicated by the X above, is actually located at a position on the slider 2| six increments beyond the numeral 9 in the row 14. Thus this slider was actually at a distance corresponding to I5. It is therefore seen that the two sliders 2| and 22 have taken care of $150 plus $4 or $154. This $154 subtracted from the $1474 remaining, shows that the slider |9 was actually positioned to accommodate $1320, with its corresponding $5.50 oi interest.

When the tens slider 2| is pushed in, to the left, the principal line 69 reads 9000K. and the i 12 interest line 29 reads $00.04. The blank space corresponding to the X, above, is actually a spot on the slider 22 one increment beyond the nu-V meral 9 in the row 88. This shows that the dollars slider 22 was taking care of $10 of the remaining $154, and that the tens slider 2| was taking care of $144 of that remainder, with its corresponding sixty cents of interest.

Finally, the positioning of the dollars slider 22 at the $10 point shows that it was taking care of only the remaining four cents oi interest.

It is on the above outlined principle that the numerals are placed on the sliders i8, I9, 2|, and and the windows are cut in the shutters 4l. 44, and 41. That is, they are so disposed that the pendent shutters 4|, 44, and 41 force the sliders next below to be pulled out a distance proportional to that portion. of the principal total which that particular slider is primarily responsible for in the completed interest calculation.

While the instant invention has been shown and described herein in what is conceived to bc the most practical and preferred embodiment, it is recognised that departures be therefrom '-.vithin the scope of the inventio which is therefore not to be limited to the details disclosed herein but is to be accorded the full scope oi' the claims.

What is claimed is:

l. Calculator comprising a cover having windows therein, a plurality of indiciabearing sliders disposed side by side for movement beneath said cover so as to selectively register the indie' thereon with said windows, at least one of sa sliders having a shutter overlying another slider between said oever and said other slider. said shutter having windows therein registrable witli one of said cover windows and with the indicia. on said other slider.

2. Calculator comprising a flat cover having a plurality of windows, a plurality of parallel elongate flat sliders disposed side by side and movable longitudinally beneath said cover and having indicia thereon registi-able with the wi dows in said cover, at least one of said slidersI having a shutter secured laterally thereto and overlying a slider on one side thereof said shutter having windows therein registrable with at least one of cover windows and with the indicia on said last mentioned slider.

3. Calculator comprising cover having win dows therein, a plurality oi indicia-bearing' sliders disposed for movement beneath said cover` as to selectively register the indicia thereon with said windows, at least one of said sliders having a first shutter overlying a slider on one side thereof between said cover and said last 'mentioned slider, and a second shutter secured thereto and overlying a slider on the other side 'thereof between said cover and said last men tioned slider, said shutters having windows therein registrable with said cover windows and with the indicia on the respective sliders which said shutters overlie.

4. Calculator for ascertaining a predeterminef.

iunction of a variable number, comprising: a iiat cover having a plurality of windows; a plurality of parallel, elongate, rlat sliders movable longitudinally beneath said cover and having indicia thereon registrable with said windows to indicate through said windows said number and said function; at least one of said sliders having a first shutter secured laterally thereto and overlying a slider on one side thereof, and a second shutter secured secured laterally thereto and overlying a slider on the other side thereof; each 13 of said shutters having windows therein registrable with the windows in said cover and with the indicia on the respective sliders over which said shutters are disposed.

5. Calculator for ascertaining interest on loans, comprising an envelope having a rectangular flat cover and a rectangular flat back spaced therefrom, said cover and back being secured together at three of their adjacent edges, the

fourth edge being open, a plurality of spacers secured to said back and interposed between said cover and said back extending from said open edge at right angles thereto, said spacers forining with said cover and back slidevvays for sliders, a plurality of fiat elongate sliders disposed in the slideways formed by said cover back and spacers, said cover having a plurality of windows therein, said sliders having numbers marked thereon registrable wtih the windows in said cover, certain of said sliders having rst shutters secured laterally thereto and overlying a slider at one side thereof, and second shutters secured laterally thereto and overlying a slider at the other side thereof, said iirst and second shutters having Windows therein registrable with the windows in said cover and with the numbers on the respective sliders which said shutters overlie.

6. Calculator ior ascertaining interest on loans, comprising an envelope having a rectangular fiat cover, a rectangular flat back spaced therefrom, said envelope being closed along three of its edges, the fourth edge being open, a plurality of spacers secured to said back and interposed between said cover and said back extending from said open edge at right angles thereto, said spacers forming with said cover and back slideways for sliders, a plurality of flat elongate sliders disposed in the slideways, said cover having at least two groups of windows therein, each group extending across said cover transversely of said sliders, one group constituting principal Windows, the other constituting interest windows, each of said sliders having two longitudinal rows of numbers thereon, one row registrable with the principal windows, the other row registrable with the interest windows, at least one of said sliders having a first shutter secured laterally thereto and overlying both the principal and interest rows of numbers on a slider at one side of said one slider, and a second shutter secured laterally thereto and overlying the interest row of numbers on a slider at the other side of said one slider, said first and second shutters having windows therein registrable with the windows in said cover and with the numbers on the respective sliders which said shutters overlie.

7. Calculator comprising a cover having two series of windows therein, one of said window series being that of a number, the other being that of a predetermined function of that number, a plurality of sliders movable beneath said cover, each slider corresponding to a denominational order of the number and having two spaced series of digits thereon, one series being a number series selectively registrable With said number window series, the other being a function series registrable with said function window series, at least one of said sliders having a shutter overlying at least the function series of digits on another slider, said shutter having a plurality of windows registrable with said function series of digits on said other slider.

Fi. Calculator according to claim i wherein said shutter overlies also the number series of digits on said other slider, and has a plurality of windows therein registrable with said number series of digits on said other slider.

9. Calculator comprising a cover having Windows therein, a plurality of elongate sliders disposed side by side and movable beneath said cover, each slider corresponding to a denominational order of a number and having digits thereon, at least one of said sliders having a shutter extending laterally therefrom and overlying at least a portion of another slider, said shutter having a plurality of Windows registrable with the digits on said other slider.

l0. interest calculator comprising a cover having two series of windows therein, one of said window series being for the principal, the other for the interest; a plurality oi sliders inovable beneath said cover, each slider corresponding to a denominational order of a principal number and having two spaced series of digits thereon, one series being a principal series selectively registrable with said principal window series, the other being an interest series registrable with said interest window series, at least one of said sliders having a shutter overlying at least the interest digit series on another slider, said shutter having a plurality or" windows registra-ble with said interest digits on said other slider.

il. Interest calculator comprising a cover having two series of windows therein, one of said window series being for the principal, the other for the interest; a plurality ot elongate sliders disposed side by side and movable beneath said cover, each slider corresponding to a denominational order of a principal number and having two spaced series of digits thereon, one series being a principal series selectively registrable with said principal window series, the other being an interest series registrable with said interest window series, at least one of said sliders having a shutter extending laterally therefrom and overlying at least the interest digit series on another slider, said shutter having a plurality oi windows registrable with said interest digit series on said other slider.

i2. Calculator nomprising a cover having a plu rality ci windows therein, at least three sliders disposed and movable side by side beneath said cover, each slider corresponding to a denominaional order of a number and having digits thereon, one of said sliders having a shutter extending laterally therefrom and overlying at least a portion of a second slider, said shutter having a plurality of windows registrable with the digits on said second slider, a third slider having a shutter extending laterally therefrom and also overlying said portion of said second slider, said third slider shutter also having a plurality oi windows registrable with the digits on said second slider.

FRANK I-I. BRXCKNER.

References Cited in the le of this patent FOREIGN PATENTS Number 

